From the photo, the glue seam did not fail. The spider fatiqued and was torn at the most vulnerable point close to the voice coil from excessive excursion (when it was completely stretched out the back and forth bend became extreme at the termination). This can be a result of simply being over-driven and abused. This can also be a result of the wrong crossover point, using bass boost or eq when you shouldn't, or an enclosure without a terminal cup and/or that was unsealed by some other means. Any woofer will have obvious distortion before it fails in that manner.

David

I installed the IB sub for now and turned down the gains a bit more. It seemed as though there were a bit too high because I could hear the non-damaged sub bottoming.

Its difficult to tune on the driveway in our neighbourhood as I dont want to play loud music for long periods of time.